A reactor is a passive element which is assembled by winding a coil on a core, and, as the core, a core (iron core) formed of a homogeneous magnetic material, or a core that is obtained by integrating a plurality of pieces of divided magnetic material by bonding or the like is used. In regard to automotive reactors or the like, the reactor assembled is housed into a case, and sealing (so-called potting) with an insulating resin or the like is performed before use, in order to eliminate the effect (especially vibrations) from the surroundings (see, for example, Patent Literature 1). On the other hand, in stationary applications such as use in the solar power system, wind power generation system, water heater with natural refrigerant heat pump, etc., the reactor is often used in a bare state without potting in the case (for example, refer to Patent Literature 2), because it is not subjected to vibration, unlike the vehicle use.
AS the material of the reactor core, silicon steel sheets containing 3 to 6.5% Si in Fe or the like materials are conventionally used. However, the silicon steel sheets are hard and poor in moldability. Therefore, application of the powder magnetic core which is obtained by compacting a soft magnetic powder having an insulating film on the surface thereof is spreading from the viewpoint of inexpensiveness and excellent moldability (for example, see Patent Literature 3).